1. Field of Invention
The present invention relates to a parallel link robot which uses a δ-type parallel link mechanism which positions an end effecter three-dimensionally. In particular, the present invention relates to a parallel link robot with an additional actuator arranged between a pair of driven links.
2. Description of Related Art
FIG. 10 is a perspective view of a parallel link robot in the prior art which is shown in Japanese Patent Publication No. 2011-88262A. In FIG. 10, a parallel link robot 100 mainly includes a base part 110 which is contained in a housing 180, a moving part 120, and three link parts 200a to 200c which link the base part 110 and the moving part 120. At the bottom surface of the moving part 120, a mounting member 190 is provided. A not shown end effecter is attached to the mounting member 190.
FIG. 11 is a partial perspective view of a parallel link robot which is shown in FIG. 10. As shown in FIG. 11, a link part 200b is comprised of a drive link 210b and two driven links 220b and 230b which extend from the moving part 120. These are linked together by spherical bearings 420b and 430b. Further, the front ends of the driven links 220b and 230b are linked by spherical bearings 440b and 450b to the moving part 120. These spherical bearings 420b to 450b are arranged so that the quadrilateral shape having these spherical bearings as vertexes becomes a parallelogram. In FIG. 10, the drive link 210b which extends from the base part 110 is connected to an actuator 130b which drives the drive link 210b. This actuator 130b is placed on the base part 110.
Referring to FIG. 11, a reinforcing link 310 links the two driven links 220b and 230b with each other through bearings. Furthermore, an additional actuator 130d is attached to a shaft 320 which extends from the center part of the reinforcing link 310 through a bearing. As shown in the figure, an output shaft of the additional actuator 130d is directed toward the moving part 120.
As shown in FIG. 11, a power transmission shaft part 390 which extends from the output shaft of the additional actuator 130d extends between the two driven links 220b and 230b in parallel with these driven links 220b and 230b. Furthermore, the power transmission shaft part 390 is connected to a shaft part 140 which extends from a posture changing mechanism part 150 through a universal joint 380. The posture changing mechanism part 150 performs the function of changing the posture of the mounting member 190. Due to this, the posture of the end effecter can be changed.
In this connection, the universal joint 380 has to be arranged on the line connecting the two spherical bearings 440b and 450b. In other words, the universal joint 380 and two spherical bearings 440b and 450b are positioned on the same line. To arrange the universal joint 380 as explained above, as shown in FIG. 11, a cutaway part C has to be formed in the edge of the moving part 120.
In general, to increase the reciprocating operations per unit time, the parallel link robot is required to operate at a high speed. To realize this, the driven links and moving part can be lightened in weight as much as possible. In this regard, when cutaway part C is formed, to secure the necessary rigidity, it is required that the moving part 120 be a certain degree of thickness. For this reason, there have been limits to the lightening of the moving part 120.
Furthermore, FIG. 12 is a cross-sectional view of a moving part in the prior art. In FIG. 12, a mounting member 190 which can rotate around a rotary shaft 590 is attached below the moving part 120. At the rotary shaft 590, a first bearing 510 and a second bearing 520 are arranged. At a front end of the rotary shaft 590, a bevel gear 550 is attached. As can be seen from FIG. 12, the bevel gear 550 of the rotary shaft 590 is engaged with a bevel gear 560 which is attached to a front end of a shaft part 140. Further, at the shaft part 140, a third bearing 530 and a fourth bearing 540 are arranged. These bevel gears 550 and 560 form a posture changing mechanism part 150.
In this connection, the modules and shapes of the bevel gears 550 and 560 are determined in accordance with the speed ratios and transmitted power of the bevel gears 550 and 560. Further, if the bevel gears 550 and 560 are determined in shape, the positional relationship between these bevel gears 550 and 560 and the universal joint 380 is determined. For this reason, the positional relationship between the top surface of the moving part 120 and the bevel gears 550 and 560 cannot be changed.
Therefore, as shown in FIG. 12, when the first bearing 510 and the second bearing 520 are arranged between the mounting member 190 and the bevel gear 550, a certain degree of space is required between the mounting member 190 and the bevel gear 550. For this reason, the casing of the moving part 120 becomes long in the axial direction of the rotary shaft 590 and the moving part 120 as a result becomes larger in size and increases in weight as well.
Further, FIG. 13 is a cross-sectional view of a moving part in another prior art. In FIG. 13, a first bearing 510 and a second bearing 520 are arranged further from a bevel gear 550 when viewed from the mounting member 190. In this case, to make the load which is applied to the first bearing 510 and the second bearing 520 smaller, the distance between the first bearing 510 and the second bearing 520 has to be made longer. Alternatively, to enable the applied load to be withstood, the first bearing 510 and the second bearing 520 themselves have to be made larger. For this reason, the casing of the moving part 120 also would become larger in size and the weights of the moving part 120 and its related members would also increase.
Furthermore, a parallel link robot is sometimes used in the fields of food, pharmaceuticals, cosmetics, etc. In such a case, due to issues with sanitation, it is necessary to prevent fluid from building up when cleaning the parallel link robot.
The present invention was made in consideration of this situation and has as its object the provision of a parallel link robot which maintains a high rigidity while being provided with a light weight moving part.